Статьи 5 семестр / Wireless networks (1)

^{Wireless Networks}

In the decade ahead, they will deliver personal­ized communications to people on the go and basic service to many who still lack telephones

by George I. Zysman

Near the end of the 19th century a young man named Guglielmo Marconi connected a spark emit­ter to a short antenna and sent a burst of radio waves through the air to a sim­ple receiver. It responded by ringing a bell, signaling the birth of a technology that promised to allow people to com­municate across distances while in mo­tion. In the closing decades of the 20th century, several waves of innovation have made wireless communications the fastest-growing segment of the glob­al telecommunications industry.

Wireless networks are proliferating rapidly, going digital and harnessing "intelligent network" technology to lo-

cate and identify roaming subscribers and to customize the services they re­ceive. An intelligent network consists of a distributed signaling network of switches, databases and dedicated com­puter servers that is separate from, yet intimately connected to, the transport networks on which subscribers' voice calls and data actually flow. This archi­tectural framework, which has been re­fined over the past 30 years to support such services as 800-number calling, caller identification and "911," will soon make personalized communications ser­vices as portable as a pocket telephone. As advances in microelectronics, dig­ital radio, signal processing and net-

work software converge in the market­place, portable telephones are getting smaller, smarter and less expensive. Some are taking on new forms, such as the wireless handheld computers called personal digital assistants (PDAs), so that they can handle text and graphics as well as audio messages; video is not far behind. Increasingly, the software running on "smart" terminals—typified by the graphical user interfaces and in­telligent software agents available to­day in PDAs—will work hand in hand with intelligent networks to enhance portable communications.

Over the past five years the demand for wireless services has risen beyond all expectations. In 1983 some industry analysts predicted that fewer than one million Americans would use cellular services by the year 2000. Currently more than 20 million do. Cellular ser­vices now spearhead the market pene­tration of wireless communications, as the number of cellular users grows an­nually by approximately 50 percent in North America, 60 percent in western Europe, 70 percent in Australia and Asia, and more than 200 percent in South America's largest markets.

Analysts now project that by 2001, three quarters of the households in the U.S. and nearly half a billion people